/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_cfft_radix4_f32.c
 * Description:  Radix-4 Decimation in Frequency CFFT & CIFFT Floating point processing function
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

extern void arm_bitreversal_f32(
	float32_t *pSrc,
	uint16_t fftSize,
	uint16_t bitRevFactor,
	const uint16_t *pBitRevTab);

void arm_radix4_butterfly_f32(
	float32_t *pSrc,
	uint16_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier);

void arm_radix4_butterfly_inverse_f32(
	float32_t *pSrc,
	uint16_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier,
	float32_t onebyfftLen);


/**
  @ingroup groupTransforms
 */

/**
  @addtogroup ComplexFFT
  @{
 */

/**
  @brief         Processing function for the floating-point Radix-4 CFFT/CIFFT.
  @deprecated    Do not use this function. It has been superseded by \ref arm_cfft_f32 and will be removed in the future.
  @param[in]     S    points to an instance of the floating-point Radix-4 CFFT/CIFFT structure
  @param[in,out] pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place
  @return        none
 */

void arm_cfft_radix4_f32(
	const arm_cfft_radix4_instance_f32 *S,
	float32_t *pSrc)
{
	if (S->ifftFlag == 1U) {
		/*  Complex IFFT radix-4  */
		arm_radix4_butterfly_inverse_f32(pSrc, S->fftLen, S->pTwiddle, S->twidCoefModifier, S->onebyfftLen);
	} else {
		/*  Complex FFT radix-4  */
		arm_radix4_butterfly_f32(pSrc, S->fftLen, S->pTwiddle, S->twidCoefModifier);
	}

	if (S->bitReverseFlag == 1U) {
		/*  Bit Reversal */
		arm_bitreversal_f32(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
	}

}

/**
  @} end of ComplexFFT group
 */

/* ----------------------------------------------------------------------
 * Internal helper function used by the FFTs
 * ---------------------------------------------------------------------- */

/**
  brief         Core function for the floating-point CFFT butterfly process.
  param[in,out] pSrc             points to the in-place buffer of floating-point data type
  param[in]     fftLen           length of the FFT
  param[in]     pCoef            points to the twiddle coefficient buffer
  param[in]     twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table
  return        none
 */

void arm_radix4_butterfly_f32(
	float32_t *pSrc,
	uint16_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier)
{
	float32_t co1, co2, co3, si1, si2, si3;
	uint32_t ia1, ia2, ia3;
	uint32_t i0, i1, i2, i3;
	uint32_t n1, n2, j, k;

#if defined (ARM_MATH_LOOPUNROLL)

	float32_t xaIn, yaIn, xbIn, ybIn, xcIn, ycIn, xdIn, ydIn;
	float32_t Xaplusc, Xbplusd, Yaplusc, Ybplusd, Xaminusc, Xbminusd, Yaminusc,
			  Ybminusd;
	float32_t Xb12C_out, Yb12C_out, Xc12C_out, Yc12C_out, Xd12C_out, Yd12C_out;
	float32_t Xb12_out, Yb12_out, Xc12_out, Yc12_out, Xd12_out, Yd12_out;
	float32_t *ptr1;
	float32_t p0, p1, p2, p3, p4, p5;
	float32_t a0, a1, a2, a3, a4, a5, a6, a7;

	/*  Initializations for the first stage */
	n2 = fftLen;
	n1 = n2;

	/* n2 = fftLen/4 */
	n2 >>= 2U;
	i0 = 0U;
	ia1 = 0U;

	j = n2;

	/*  Calculation of first stage */
	do {
		/*  index calculation for the input as, */
		/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
		i1 = i0 + n2;
		i2 = i1 + n2;
		i3 = i2 + n2;

		xaIn = pSrc[(2U * i0)];
		yaIn = pSrc[(2U * i0) + 1U];

		xbIn = pSrc[(2U * i1)];
		ybIn = pSrc[(2U * i1) + 1U];

		xcIn = pSrc[(2U * i2)];
		ycIn = pSrc[(2U * i2) + 1U];

		xdIn = pSrc[(2U * i3)];
		ydIn = pSrc[(2U * i3) + 1U];

		/* xa + xc */
		Xaplusc = xaIn + xcIn;
		/* xb + xd */
		Xbplusd = xbIn + xdIn;
		/* ya + yc */
		Yaplusc = yaIn + ycIn;
		/* yb + yd */
		Ybplusd = ybIn + ydIn;

		/*  index calculation for the coefficients */
		ia2 = ia1 + ia1;
		co2 = pCoef[ia2 * 2U];
		si2 = pCoef[(ia2 * 2U) + 1U];

		/* xa - xc */
		Xaminusc = xaIn - xcIn;
		/* xb - xd */
		Xbminusd = xbIn - xdIn;
		/* ya - yc */
		Yaminusc = yaIn - ycIn;
		/* yb - yd */
		Ybminusd = ybIn - ydIn;

		/* xa' = xa + xb + xc + xd */
		pSrc[(2U * i0)] = Xaplusc + Xbplusd;
		/* ya' = ya + yb + yc + yd */
		pSrc[(2U * i0) + 1U] = Yaplusc + Ybplusd;

		/* (xa - xc) + (yb - yd) */
		Xb12C_out = (Xaminusc + Ybminusd);
		/* (ya - yc) + (xb - xd) */
		Yb12C_out = (Yaminusc - Xbminusd);
		/* (xa + xc) - (xb + xd) */
		Xc12C_out = (Xaplusc - Xbplusd);
		/* (ya + yc) - (yb + yd) */
		Yc12C_out = (Yaplusc - Ybplusd);
		/* (xa - xc) - (yb - yd) */
		Xd12C_out = (Xaminusc - Ybminusd);
		/* (ya - yc) + (xb - xd) */
		Yd12C_out = (Xbminusd + Yaminusc);

		co1 = pCoef[ia1 * 2U];
		si1 = pCoef[(ia1 * 2U) + 1U];

		/*  index calculation for the coefficients */
		ia3 = ia2 + ia1;
		co3 = pCoef[ia3 * 2U];
		si3 = pCoef[(ia3 * 2U) + 1U];

		Xb12_out = Xb12C_out * co1;
		Yb12_out = Yb12C_out * co1;
		Xc12_out = Xc12C_out * co2;
		Yc12_out = Yc12C_out * co2;
		Xd12_out = Xd12C_out * co3;
		Yd12_out = Yd12C_out * co3;

		/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
		//Xb12_out -= Yb12C_out * si1;
		p0 = Yb12C_out * si1;
		/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
		//Yb12_out += Xb12C_out * si1;
		p1 = Xb12C_out * si1;
		/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
		//Xc12_out -= Yc12C_out * si2;
		p2 = Yc12C_out * si2;
		/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
		//Yc12_out += Xc12C_out * si2;
		p3 = Xc12C_out * si2;
		/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
		//Xd12_out -= Yd12C_out * si3;
		p4 = Yd12C_out * si3;
		/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
		//Yd12_out += Xd12C_out * si3;
		p5 = Xd12C_out * si3;

		Xb12_out += p0;
		Yb12_out -= p1;
		Xc12_out += p2;
		Yc12_out -= p3;
		Xd12_out += p4;
		Yd12_out -= p5;

		/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */
		pSrc[2U * i1] = Xc12_out;

		/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */
		pSrc[(2U * i1) + 1U] = Yc12_out;

		/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */
		pSrc[2U * i2] = Xb12_out;

		/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */
		pSrc[(2U * i2) + 1U] = Yb12_out;

		/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */
		pSrc[2U * i3] = Xd12_out;

		/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */
		pSrc[(2U * i3) + 1U] = Yd12_out;

		/*  Twiddle coefficients index modifier */
		ia1 += twidCoefModifier;

		/*  Updating input index */
		i0++;

	} while (--j);

	twidCoefModifier <<= 2U;

	/*  Calculation of second stage to excluding last stage */
	for (k = fftLen >> 2U; k > 4U; k >>= 2U) {
		/*  Initializations for the first stage */
		n1 = n2;
		n2 >>= 2U;
		ia1 = 0U;

		/*  Calculation of first stage */
		j = 0;
		do {
			/*  index calculation for the coefficients */
			ia2 = ia1 + ia1;
			ia3 = ia2 + ia1;
			co1 = pCoef[(ia1 * 2U)];
			si1 = pCoef[(ia1 * 2U) + 1U];
			co2 = pCoef[(ia2 * 2U)];
			si2 = pCoef[(ia2 * 2U) + 1U];
			co3 = pCoef[(ia3 * 2U)];
			si3 = pCoef[(ia3 * 2U) + 1U];

			/*  Twiddle coefficients index modifier */
			ia1 += twidCoefModifier;

			i0 = j;
			do {
				/*  index calculation for the input as, */
				/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
				i1 = i0 + n2;
				i2 = i1 + n2;
				i3 = i2 + n2;

				xaIn = pSrc[(2U * i0)];
				yaIn = pSrc[(2U * i0) + 1U];

				xbIn = pSrc[(2U * i1)];
				ybIn = pSrc[(2U * i1) + 1U];

				xcIn = pSrc[(2U * i2)];
				ycIn = pSrc[(2U * i2) + 1U];

				xdIn = pSrc[(2U * i3)];
				ydIn = pSrc[(2U * i3) + 1U];

				/* xa - xc */
				Xaminusc = xaIn - xcIn;
				/* (xb - xd) */
				Xbminusd = xbIn - xdIn;
				/* ya - yc */
				Yaminusc = yaIn - ycIn;
				/* (yb - yd) */
				Ybminusd = ybIn - ydIn;

				/* xa + xc */
				Xaplusc = xaIn + xcIn;
				/* xb + xd */
				Xbplusd = xbIn + xdIn;
				/* ya + yc */
				Yaplusc = yaIn + ycIn;
				/* yb + yd */
				Ybplusd = ybIn + ydIn;

				/* (xa - xc) + (yb - yd) */
				Xb12C_out = (Xaminusc + Ybminusd);
				/* (ya - yc) -  (xb - xd) */
				Yb12C_out = (Yaminusc - Xbminusd);
				/* xa + xc -(xb + xd) */
				Xc12C_out = (Xaplusc - Xbplusd);
				/* (ya + yc) - (yb + yd) */
				Yc12C_out = (Yaplusc - Ybplusd);
				/* (xa - xc) - (yb - yd) */
				Xd12C_out = (Xaminusc - Ybminusd);
				/* (ya - yc) +  (xb - xd) */
				Yd12C_out = (Xbminusd + Yaminusc);

				pSrc[(2U * i0)] = Xaplusc + Xbplusd;
				pSrc[(2U * i0) + 1U] = Yaplusc + Ybplusd;

				Xb12_out = Xb12C_out * co1;
				Yb12_out = Yb12C_out * co1;
				Xc12_out = Xc12C_out * co2;
				Yc12_out = Yc12C_out * co2;
				Xd12_out = Xd12C_out * co3;
				Yd12_out = Yd12C_out * co3;

				/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
				//Xb12_out -= Yb12C_out * si1;
				p0 = Yb12C_out * si1;
				/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
				//Yb12_out += Xb12C_out * si1;
				p1 = Xb12C_out * si1;
				/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
				//Xc12_out -= Yc12C_out * si2;
				p2 = Yc12C_out * si2;
				/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
				//Yc12_out += Xc12C_out * si2;
				p3 = Xc12C_out * si2;
				/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
				//Xd12_out -= Yd12C_out * si3;
				p4 = Yd12C_out * si3;
				/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
				//Yd12_out += Xd12C_out * si3;
				p5 = Xd12C_out * si3;

				Xb12_out += p0;
				Yb12_out -= p1;
				Xc12_out += p2;
				Yc12_out -= p3;
				Xd12_out += p4;
				Yd12_out -= p5;

				/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */
				pSrc[2U * i1] = Xc12_out;

				/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */
				pSrc[(2U * i1) + 1U] = Yc12_out;

				/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */
				pSrc[2U * i2] = Xb12_out;

				/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */
				pSrc[(2U * i2) + 1U] = Yb12_out;

				/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */
				pSrc[2U * i3] = Xd12_out;

				/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */
				pSrc[(2U * i3) + 1U] = Yd12_out;

				i0 += n1;
			} while (i0 < fftLen);
			j++;
		} while (j <= (n2 - 1U));
		twidCoefModifier <<= 2U;
	}

	j = fftLen >> 2;
	ptr1 = &pSrc[0];

	/*  Calculations of last stage */
	do {
		xaIn = ptr1[0];
		yaIn = ptr1[1];
		xbIn = ptr1[2];
		ybIn = ptr1[3];
		xcIn = ptr1[4];
		ycIn = ptr1[5];
		xdIn = ptr1[6];
		ydIn = ptr1[7];

		/* xa + xc */
		Xaplusc = xaIn + xcIn;

		/* xa - xc */
		Xaminusc = xaIn - xcIn;

		/* ya + yc */
		Yaplusc = yaIn + ycIn;

		/* ya - yc */
		Yaminusc = yaIn - ycIn;

		/* xb + xd */
		Xbplusd = xbIn + xdIn;

		/* yb + yd */
		Ybplusd = ybIn + ydIn;

		/* (xb-xd) */
		Xbminusd = xbIn - xdIn;

		/* (yb-yd) */
		Ybminusd = ybIn - ydIn;

		/* xa' = xa + xb + xc + xd */
		a0 = (Xaplusc + Xbplusd);
		/* ya' = ya + yb + yc + yd */
		a1 = (Yaplusc + Ybplusd);
		/* xc' = (xa-xb+xc-xd) */
		a2 = (Xaplusc - Xbplusd);
		/* yc' = (ya-yb+yc-yd) */
		a3 = (Yaplusc - Ybplusd);
		/* xb' = (xa+yb-xc-yd) */
		a4 = (Xaminusc + Ybminusd);
		/* yb' = (ya-xb-yc+xd) */
		a5 = (Yaminusc - Xbminusd);
		/* xd' = (xa-yb-xc+yd)) */
		a6 = (Xaminusc - Ybminusd);
		/* yd' = (ya+xb-yc-xd) */
		a7 = (Xbminusd + Yaminusc);

		ptr1[0] = a0;
		ptr1[1] = a1;
		ptr1[2] = a2;
		ptr1[3] = a3;
		ptr1[4] = a4;
		ptr1[5] = a5;
		ptr1[6] = a6;
		ptr1[7] = a7;

		/* increment pointer by 8 */
		ptr1 += 8U;
	} while (--j);

#else

	float32_t t1, t2, r1, r2, s1, s2;

	/* Initializations for the fft calculation */
	n2 = fftLen;
	n1 = n2;
	for (k = fftLen; k > 1U; k >>= 2U) {
		/*  Initializations for the fft calculation */
		n1 = n2;
		n2 >>= 2U;
		ia1 = 0U;

		/*  FFT Calculation */
		j = 0;
		do {
			/*  index calculation for the coefficients */
			ia2 = ia1 + ia1;
			ia3 = ia2 + ia1;
			co1 = pCoef[ia1 * 2U];
			si1 = pCoef[(ia1 * 2U) + 1U];
			co2 = pCoef[ia2 * 2U];
			si2 = pCoef[(ia2 * 2U) + 1U];
			co3 = pCoef[ia3 * 2U];
			si3 = pCoef[(ia3 * 2U) + 1U];

			/*  Twiddle coefficients index modifier */
			ia1 = ia1 + twidCoefModifier;

			i0 = j;
			do {
				/*  index calculation for the input as, */
				/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
				i1 = i0 + n2;
				i2 = i1 + n2;
				i3 = i2 + n2;

				/* xa + xc */
				r1 = pSrc[(2U * i0)] + pSrc[(2U * i2)];

				/* xa - xc */
				r2 = pSrc[(2U * i0)] - pSrc[(2U * i2)];

				/* ya + yc */
				s1 = pSrc[(2U * i0) + 1U] + pSrc[(2U * i2) + 1U];

				/* ya - yc */
				s2 = pSrc[(2U * i0) + 1U] - pSrc[(2U * i2) + 1U];

				/* xb + xd */
				t1 = pSrc[2U * i1] + pSrc[2U * i3];

				/* xa' = xa + xb + xc + xd */
				pSrc[2U * i0] = r1 + t1;

				/* xa + xc -(xb + xd) */
				r1 = r1 - t1;

				/* yb + yd */
				t2 = pSrc[(2U * i1) + 1U] + pSrc[(2U * i3) + 1U];

				/* ya' = ya + yb + yc + yd */
				pSrc[(2U * i0) + 1U] = s1 + t2;

				/* (ya + yc) - (yb + yd) */
				s1 = s1 - t2;

				/* (yb - yd) */
				t1 = pSrc[(2U * i1) + 1U] - pSrc[(2U * i3) + 1U];

				/* (xb - xd) */
				t2 = pSrc[2U * i1] - pSrc[2U * i3];

				/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */
				pSrc[2U * i1] = (r1 * co2) + (s1 * si2);

				/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */
				pSrc[(2U * i1) + 1U] = (s1 * co2) - (r1 * si2);

				/* (xa - xc) + (yb - yd) */
				r1 = r2 + t1;

				/* (xa - xc) - (yb - yd) */
				r2 = r2 - t1;

				/* (ya - yc) -  (xb - xd) */
				s1 = s2 - t2;

				/* (ya - yc) +  (xb - xd) */
				s2 = s2 + t2;

				/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */
				pSrc[2U * i2] = (r1 * co1) + (s1 * si1);

				/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */
				pSrc[(2U * i2) + 1U] = (s1 * co1) - (r1 * si1);

				/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */
				pSrc[2U * i3] = (r2 * co3) + (s2 * si3);

				/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */
				pSrc[(2U * i3) + 1U] = (s2 * co3) - (r2 * si3);

				i0 += n1;
			} while (i0 < fftLen);
			j++;
		} while (j <= (n2 - 1U));
		twidCoefModifier <<= 2U;
	}

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

}

/**
  brief         Core function for the floating-point CIFFT butterfly process.
  param[in,out] pSrc             points to the in-place buffer of floating-point data type
  param[in]     fftLen           length of the FFT
  param[in]     pCoef            points to twiddle coefficient buffer
  param[in]     twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
  param[in]     onebyfftLen      value of 1/fftLen
  return        none
 */

void arm_radix4_butterfly_inverse_f32(
	float32_t *pSrc,
	uint16_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier,
	float32_t onebyfftLen)
{
	float32_t co1, co2, co3, si1, si2, si3;
	uint32_t ia1, ia2, ia3;
	uint32_t i0, i1, i2, i3;
	uint32_t n1, n2, j, k;

#if defined (ARM_MATH_LOOPUNROLL)

	float32_t xaIn, yaIn, xbIn, ybIn, xcIn, ycIn, xdIn, ydIn;
	float32_t Xaplusc, Xbplusd, Yaplusc, Ybplusd, Xaminusc, Xbminusd, Yaminusc,
			  Ybminusd;
	float32_t Xb12C_out, Yb12C_out, Xc12C_out, Yc12C_out, Xd12C_out, Yd12C_out;
	float32_t Xb12_out, Yb12_out, Xc12_out, Yc12_out, Xd12_out, Yd12_out;
	float32_t *ptr1;
	float32_t p0, p1, p2, p3, p4, p5, p6, p7;
	float32_t a0, a1, a2, a3, a4, a5, a6, a7;


	/*  Initializations for the first stage */
	n2 = fftLen;
	n1 = n2;

	/* n2 = fftLen/4 */
	n2 >>= 2U;
	i0 = 0U;
	ia1 = 0U;

	j = n2;

	/*  Calculation of first stage */
	do {
		/*  index calculation for the input as, */
		/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
		i1 = i0 + n2;
		i2 = i1 + n2;
		i3 = i2 + n2;

		/*  Butterfly implementation */
		xaIn = pSrc[(2U * i0)];
		yaIn = pSrc[(2U * i0) + 1U];

		xcIn = pSrc[(2U * i2)];
		ycIn = pSrc[(2U * i2) + 1U];

		xbIn = pSrc[(2U * i1)];
		ybIn = pSrc[(2U * i1) + 1U];

		xdIn = pSrc[(2U * i3)];
		ydIn = pSrc[(2U * i3) + 1U];

		/* xa + xc */
		Xaplusc = xaIn + xcIn;
		/* xb + xd */
		Xbplusd = xbIn + xdIn;
		/* ya + yc */
		Yaplusc = yaIn + ycIn;
		/* yb + yd */
		Ybplusd = ybIn + ydIn;

		/*  index calculation for the coefficients */
		ia2 = ia1 + ia1;
		co2 = pCoef[ia2 * 2U];
		si2 = pCoef[(ia2 * 2U) + 1U];

		/* xa - xc */
		Xaminusc = xaIn - xcIn;
		/* xb - xd */
		Xbminusd = xbIn - xdIn;
		/* ya - yc */
		Yaminusc = yaIn - ycIn;
		/* yb - yd */
		Ybminusd = ybIn - ydIn;

		/* xa' = xa + xb + xc + xd */
		pSrc[(2U * i0)] = Xaplusc + Xbplusd;

		/* ya' = ya + yb + yc + yd */
		pSrc[(2U * i0) + 1U] = Yaplusc + Ybplusd;

		/* (xa - xc) - (yb - yd) */
		Xb12C_out = (Xaminusc - Ybminusd);
		/* (ya - yc) + (xb - xd) */
		Yb12C_out = (Yaminusc + Xbminusd);
		/* (xa + xc) - (xb + xd) */
		Xc12C_out = (Xaplusc - Xbplusd);
		/* (ya + yc) - (yb + yd) */
		Yc12C_out = (Yaplusc - Ybplusd);
		/* (xa - xc) + (yb - yd) */
		Xd12C_out = (Xaminusc + Ybminusd);
		/* (ya - yc) - (xb - xd) */
		Yd12C_out = (Yaminusc - Xbminusd);

		co1 = pCoef[ia1 * 2U];
		si1 = pCoef[(ia1 * 2U) + 1U];

		/*  index calculation for the coefficients */
		ia3 = ia2 + ia1;
		co3 = pCoef[ia3 * 2U];
		si3 = pCoef[(ia3 * 2U) + 1U];

		Xb12_out = Xb12C_out * co1;
		Yb12_out = Yb12C_out * co1;
		Xc12_out = Xc12C_out * co2;
		Yc12_out = Yc12C_out * co2;
		Xd12_out = Xd12C_out * co3;
		Yd12_out = Yd12C_out * co3;

		/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
		//Xb12_out -= Yb12C_out * si1;
		p0 = Yb12C_out * si1;
		/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
		//Yb12_out += Xb12C_out * si1;
		p1 = Xb12C_out * si1;
		/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
		//Xc12_out -= Yc12C_out * si2;
		p2 = Yc12C_out * si2;
		/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
		//Yc12_out += Xc12C_out * si2;
		p3 = Xc12C_out * si2;
		/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
		//Xd12_out -= Yd12C_out * si3;
		p4 = Yd12C_out * si3;
		/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
		//Yd12_out += Xd12C_out * si3;
		p5 = Xd12C_out * si3;

		Xb12_out -= p0;
		Yb12_out += p1;
		Xc12_out -= p2;
		Yc12_out += p3;
		Xd12_out -= p4;
		Yd12_out += p5;

		/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
		pSrc[2U * i1] = Xc12_out;

		/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
		pSrc[(2U * i1) + 1U] = Yc12_out;

		/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
		pSrc[2U * i2] = Xb12_out;

		/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
		pSrc[(2U * i2) + 1U] = Yb12_out;

		/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
		pSrc[2U * i3] = Xd12_out;

		/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
		pSrc[(2U * i3) + 1U] = Yd12_out;

		/*  Twiddle coefficients index modifier */
		ia1 = ia1 + twidCoefModifier;

		/*  Updating input index */
		i0 = i0 + 1U;

	} while (--j);

	twidCoefModifier <<= 2U;

	/*  Calculation of second stage to excluding last stage */
	for (k = fftLen >> 2U; k > 4U; k >>= 2U) {
		/*  Initializations for the first stage */
		n1 = n2;
		n2 >>= 2U;
		ia1 = 0U;

		/*  Calculation of first stage */
		j = 0;
		do {
			/*  index calculation for the coefficients */
			ia2 = ia1 + ia1;
			ia3 = ia2 + ia1;
			co1 = pCoef[ia1 * 2U];
			si1 = pCoef[(ia1 * 2U) + 1U];
			co2 = pCoef[ia2 * 2U];
			si2 = pCoef[(ia2 * 2U) + 1U];
			co3 = pCoef[ia3 * 2U];
			si3 = pCoef[(ia3 * 2U) + 1U];

			/*  Twiddle coefficients index modifier */
			ia1 = ia1 + twidCoefModifier;

			i0 = j;
			do {
				/*  index calculation for the input as, */
				/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
				i1 = i0 + n2;
				i2 = i1 + n2;
				i3 = i2 + n2;

				xaIn = pSrc[(2U * i0)];
				yaIn = pSrc[(2U * i0) + 1U];

				xbIn = pSrc[(2U * i1)];
				ybIn = pSrc[(2U * i1) + 1U];

				xcIn = pSrc[(2U * i2)];
				ycIn = pSrc[(2U * i2) + 1U];

				xdIn = pSrc[(2U * i3)];
				ydIn = pSrc[(2U * i3) + 1U];

				/* xa - xc */
				Xaminusc = xaIn - xcIn;
				/* (xb - xd) */
				Xbminusd = xbIn - xdIn;
				/* ya - yc */
				Yaminusc = yaIn - ycIn;
				/* (yb - yd) */
				Ybminusd = ybIn - ydIn;

				/* xa + xc */
				Xaplusc = xaIn + xcIn;
				/* xb + xd */
				Xbplusd = xbIn + xdIn;
				/* ya + yc */
				Yaplusc = yaIn + ycIn;
				/* yb + yd */
				Ybplusd = ybIn + ydIn;

				/* (xa - xc) - (yb - yd) */
				Xb12C_out = (Xaminusc - Ybminusd);
				/* (ya - yc) +  (xb - xd) */
				Yb12C_out = (Yaminusc + Xbminusd);
				/* xa + xc -(xb + xd) */
				Xc12C_out = (Xaplusc - Xbplusd);
				/* (ya + yc) - (yb + yd) */
				Yc12C_out = (Yaplusc - Ybplusd);
				/* (xa - xc) + (yb - yd) */
				Xd12C_out = (Xaminusc + Ybminusd);
				/* (ya - yc) -  (xb - xd) */
				Yd12C_out = (Yaminusc - Xbminusd);

				pSrc[(2U * i0)] = Xaplusc + Xbplusd;
				pSrc[(2U * i0) + 1U] = Yaplusc + Ybplusd;

				Xb12_out = Xb12C_out * co1;
				Yb12_out = Yb12C_out * co1;
				Xc12_out = Xc12C_out * co2;
				Yc12_out = Yc12C_out * co2;
				Xd12_out = Xd12C_out * co3;
				Yd12_out = Yd12C_out * co3;

				/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
				//Xb12_out -= Yb12C_out * si1;
				p0 = Yb12C_out * si1;
				/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
				//Yb12_out += Xb12C_out * si1;
				p1 = Xb12C_out * si1;
				/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
				//Xc12_out -= Yc12C_out * si2;
				p2 = Yc12C_out * si2;
				/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
				//Yc12_out += Xc12C_out * si2;
				p3 = Xc12C_out * si2;
				/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
				//Xd12_out -= Yd12C_out * si3;
				p4 = Yd12C_out * si3;
				/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
				//Yd12_out += Xd12C_out * si3;
				p5 = Xd12C_out * si3;

				Xb12_out -= p0;
				Yb12_out += p1;
				Xc12_out -= p2;
				Yc12_out += p3;
				Xd12_out -= p4;
				Yd12_out += p5;

				/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
				pSrc[2U * i1] = Xc12_out;

				/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
				pSrc[(2U * i1) + 1U] = Yc12_out;

				/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
				pSrc[2U * i2] = Xb12_out;

				/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
				pSrc[(2U * i2) + 1U] = Yb12_out;

				/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
				pSrc[2U * i3] = Xd12_out;

				/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
				pSrc[(2U * i3) + 1U] = Yd12_out;

				i0 += n1;
			} while (i0 < fftLen);
			j++;
		} while (j <= (n2 - 1U));
		twidCoefModifier <<= 2U;
	}
	/*  Initializations of last stage */

	j = fftLen >> 2;
	ptr1 = &pSrc[0];

	/*  Calculations of last stage */
	do {
		xaIn = ptr1[0];
		yaIn = ptr1[1];
		xbIn = ptr1[2];
		ybIn = ptr1[3];
		xcIn = ptr1[4];
		ycIn = ptr1[5];
		xdIn = ptr1[6];
		ydIn = ptr1[7];

		/*  Butterfly implementation */
		/* xa + xc */
		Xaplusc = xaIn + xcIn;

		/* xa - xc */
		Xaminusc = xaIn - xcIn;

		/* ya + yc */
		Yaplusc = yaIn + ycIn;

		/* ya - yc */
		Yaminusc = yaIn - ycIn;

		/* xb + xd */
		Xbplusd = xbIn + xdIn;

		/* yb + yd */
		Ybplusd = ybIn + ydIn;

		/* (xb-xd) */
		Xbminusd = xbIn - xdIn;

		/* (yb-yd) */
		Ybminusd = ybIn - ydIn;

		/* xa' = (xa+xb+xc+xd) * onebyfftLen */
		a0 = (Xaplusc + Xbplusd);
		/* ya' = (ya+yb+yc+yd) * onebyfftLen */
		a1 = (Yaplusc + Ybplusd);
		/* xc' = (xa-xb+xc-xd) * onebyfftLen */
		a2 = (Xaplusc - Xbplusd);
		/* yc' = (ya-yb+yc-yd) * onebyfftLen  */
		a3 = (Yaplusc - Ybplusd);
		/* xb' = (xa-yb-xc+yd) * onebyfftLen */
		a4 = (Xaminusc - Ybminusd);
		/* yb' = (ya+xb-yc-xd) * onebyfftLen */
		a5 = (Yaminusc + Xbminusd);
		/* xd' = (xa-yb-xc+yd) * onebyfftLen */
		a6 = (Xaminusc + Ybminusd);
		/* yd' = (ya-xb-yc+xd) * onebyfftLen */
		a7 = (Yaminusc - Xbminusd);

		p0 = a0 * onebyfftLen;
		p1 = a1 * onebyfftLen;
		p2 = a2 * onebyfftLen;
		p3 = a3 * onebyfftLen;
		p4 = a4 * onebyfftLen;
		p5 = a5 * onebyfftLen;
		p6 = a6 * onebyfftLen;
		p7 = a7 * onebyfftLen;

		/* xa' = (xa+xb+xc+xd) * onebyfftLen */
		ptr1[0] = p0;
		/* ya' = (ya+yb+yc+yd) * onebyfftLen */
		ptr1[1] = p1;
		/* xc' = (xa-xb+xc-xd) * onebyfftLen */
		ptr1[2] = p2;
		/* yc' = (ya-yb+yc-yd) * onebyfftLen  */
		ptr1[3] = p3;
		/* xb' = (xa-yb-xc+yd) * onebyfftLen */
		ptr1[4] = p4;
		/* yb' = (ya+xb-yc-xd) * onebyfftLen */
		ptr1[5] = p5;
		/* xd' = (xa-yb-xc+yd) * onebyfftLen */
		ptr1[6] = p6;
		/* yd' = (ya-xb-yc+xd) * onebyfftLen */
		ptr1[7] = p7;

		/* increment source pointer by 8 for next calculations */
		ptr1 = ptr1 + 8U;

	} while (--j);

#else

	float32_t t1, t2, r1, r2, s1, s2;

	/*  Initializations for the first stage */
	n2 = fftLen;
	n1 = n2;

	/*  Calculation of first stage */
	for (k = fftLen; k > 4U; k >>= 2U) {
		/*  Initializations for the first stage */
		n1 = n2;
		n2 >>= 2U;
		ia1 = 0U;

		/*  Calculation of first stage */
		j = 0;
		do {
			/*  index calculation for the coefficients */
			ia2 = ia1 + ia1;
			ia3 = ia2 + ia1;
			co1 = pCoef[ia1 * 2U];
			si1 = pCoef[(ia1 * 2U) + 1U];
			co2 = pCoef[ia2 * 2U];
			si2 = pCoef[(ia2 * 2U) + 1U];
			co3 = pCoef[ia3 * 2U];
			si3 = pCoef[(ia3 * 2U) + 1U];

			/*  Twiddle coefficients index modifier */
			ia1 = ia1 + twidCoefModifier;

			i0 = j;
			do {
				/*  index calculation for the input as, */
				/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
				i1 = i0 + n2;
				i2 = i1 + n2;
				i3 = i2 + n2;

				/* xa + xc */
				r1 = pSrc[(2U * i0)] + pSrc[(2U * i2)];

				/* xa - xc */
				r2 = pSrc[(2U * i0)] - pSrc[(2U * i2)];

				/* ya + yc */
				s1 = pSrc[(2U * i0) + 1U] + pSrc[(2U * i2) + 1U];

				/* ya - yc */
				s2 = pSrc[(2U * i0) + 1U] - pSrc[(2U * i2) + 1U];

				/* xb + xd */
				t1 = pSrc[2U * i1] + pSrc[2U * i3];

				/* xa' = xa + xb + xc + xd */
				pSrc[2U * i0] = r1 + t1;

				/* xa + xc -(xb + xd) */
				r1 = r1 - t1;

				/* yb + yd */
				t2 = pSrc[(2U * i1) + 1U] + pSrc[(2U * i3) + 1U];

				/* ya' = ya + yb + yc + yd */
				pSrc[(2U * i0) + 1U] = s1 + t2;

				/* (ya + yc) - (yb + yd) */
				s1 = s1 - t2;

				/* (yb - yd) */
				t1 = pSrc[(2U * i1) + 1U] - pSrc[(2U * i3) + 1U];

				/* (xb - xd) */
				t2 = pSrc[2U * i1] - pSrc[2U * i3];

				/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
				pSrc[2U * i1] = (r1 * co2) - (s1 * si2);

				/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
				pSrc[(2U * i1) + 1U] = (s1 * co2) + (r1 * si2);

				/* (xa - xc) - (yb - yd) */
				r1 = r2 - t1;

				/* (xa - xc) + (yb - yd) */
				r2 = r2 + t1;

				/* (ya - yc) +  (xb - xd) */
				s1 = s2 + t2;

				/* (ya - yc) -  (xb - xd) */
				s2 = s2 - t2;

				/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
				pSrc[2U * i2] = (r1 * co1) - (s1 * si1);

				/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
				pSrc[(2U * i2) + 1U] = (s1 * co1) + (r1 * si1);

				/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
				pSrc[2U * i3] = (r2 * co3) - (s2 * si3);

				/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
				pSrc[(2U * i3) + 1U] = (s2 * co3) + (r2 * si3);

				i0 += n1;
			} while (i0 < fftLen);
			j++;
		} while (j <= (n2 - 1U));
		twidCoefModifier <<= 2U;
	}
	/*  Initializations of last stage */
	n1 = n2;
	n2 >>= 2U;

	/*  Calculations of last stage */
	for (i0 = 0U; i0 <= (fftLen - n1); i0 += n1) {
		/*  index calculation for the input as, */
		/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
		i1 = i0 + n2;
		i2 = i1 + n2;
		i3 = i2 + n2;

		/*  Butterfly implementation */
		/* xa + xc */
		r1 = pSrc[2U * i0] + pSrc[2U * i2];

		/* xa - xc */
		r2 = pSrc[2U * i0] - pSrc[2U * i2];

		/* ya + yc */
		s1 = pSrc[(2U * i0) + 1U] + pSrc[(2U * i2) + 1U];

		/* ya - yc */
		s2 = pSrc[(2U * i0) + 1U] - pSrc[(2U * i2) + 1U];

		/* xc + xd */
		t1 = pSrc[2U * i1] + pSrc[2U * i3];

		/* xa' = xa + xb + xc + xd */
		pSrc[2U * i0] = (r1 + t1) * onebyfftLen;

		/* (xa + xb) - (xc + xd) */
		r1 = r1 - t1;

		/* yb + yd */
		t2 = pSrc[(2U * i1) + 1U] + pSrc[(2U * i3) + 1U];

		/* ya' = ya + yb + yc + yd */
		pSrc[(2U * i0) + 1U] = (s1 + t2) * onebyfftLen;

		/* (ya + yc) - (yb + yd) */
		s1 = s1 - t2;

		/* (yb-yd) */
		t1 = pSrc[(2U * i1) + 1U] - pSrc[(2U * i3) + 1U];

		/* (xb-xd) */
		t2 = pSrc[2U * i1] - pSrc[2U * i3];

		/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
		pSrc[2U * i1] = r1 * onebyfftLen;

		/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
		pSrc[(2U * i1) + 1U] = s1 * onebyfftLen;

		/* (xa - xc) - (yb-yd) */
		r1 = r2 - t1;

		/* (xa - xc) + (yb-yd) */
		r2 = r2 + t1;

		/* (ya - yc) + (xb-xd) */
		s1 = s2 + t2;

		/* (ya - yc) - (xb-xd) */
		s2 = s2 - t2;

		/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
		pSrc[2U * i2] = r1 * onebyfftLen;

		/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
		pSrc[(2U * i2) + 1U] = s1 * onebyfftLen;

		/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
		pSrc[2U * i3] = r2 * onebyfftLen;

		/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
		pSrc[(2U * i3) + 1U] = s2 * onebyfftLen;
	}

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
}


